Dataset Information

The origin of ?-strand bending in globular proteins.

ABSTRACT: Many ?-strands are not flat but bend and/or twist. However, although almost all ?-strands have a twist, not all have a bend, suggesting that the underlying force(s) driving ?-strand bending is distinct from that for the twist. We, therefore, investigated the physical origin(s) of ?-strand bends.We calculated rotation, twist and bend angles for a four-residue short frame. Fixed-length fragments consisting of six residues found in three consecutive short frames were used to evaluate the twist and bend angles of full-length ?-strands.We calculated and statistically analyzed the twist and bend angles of ?-strands found in globular proteins with known three-dimensional structures. The results show that full-length ?-strand bend angles are related to the nearby aromatic residue content, whereas local bend angles are related to the nearby aliphatic residue content. Furthermore, it appears that ?-strands bend to maximize their hydrophobic contacts with an abutting hydrophobic surface or to form a hydrophobic side-chain cluster when an abutting hydrophobic surface is absent.We conclude that the dominant driving force for full-length ?-strand bends is the hydrophobic interaction involving aromatic residues, whereas that for local ?-strand bends is the hydrophobic interaction involving aliphatic residues.

SUBMITTER: Fujiwara K

PROVIDER: S-EPMC4618951 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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The origin of β-strand bending in globular proteins.

Fujiwara Kazuo K Ebisawa Shinichi S Watanabe Yuka Y Fujiwara Hiromi H Ikeguchi Masamichi M

BMC structural biology 20151022

<h4>Background</h4>Many β-strands are not flat but bend and/or twist. However, although almost all β-strands have a twist, not all have a bend, suggesting that the underlying force(s) driving β-strand bending is distinct from that for the twist. We, therefore, investigated the physical origin(s) of β-strand bends.<h4>Methods</h4>We calculated rotation, twist and bend angles for a four-residue short frame. Fixed-length fragments consisting of six residues found in three consecutive short frames w ...[more]

PMID: 26492857

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Project description:Experiments show that for many two-state folders the free energy of the native state, DeltaG(ND)([C]), changes linearly as the denaturant concentration, [C], is varied. The slope {m = [dDeltaG(ND)([C])]/(d[C])}, is nearly constant. According to the transfer model, the m-value is associated with the difference in the surface area between the native (N) and denatured (D) state, which should be a function of DeltaR(g)(2), the difference in the square of the radius of gyration between the D and N states. Single-molecule experiments show that the R(g) of the structurally heterogeneous denatured state undergoes an equilibrium collapse transition as [C] decreases, which implies m also should be [C]-dependent. We resolve the conundrum between constant m-values and [C]-dependent changes in R(g) using molecular simulations of a coarse-grained representation of protein L, and the molecular transfer model, for which the equilibrium folding can be accurately calculated as a function of denaturant (urea) concentration. In agreement with experiment, we find that over a large range of denaturant concentration (>3 M) the m-value is a constant, whereas under strongly renaturing conditions (<3 M), it depends on [C]. The m-value is a constant above [C] > 3 M because the [C]-dependent changes in the surface area of the backbone groups, which make the largest contribution to m, are relatively narrow in the denatured state. The burial of the backbone and hydrophobic side chains gives rise to substantial surface area changes below [C] < 3 M, leading to collapse in the denatured state of protein L. Dissection of the contribution of various amino acids to the total surface area change with [C] shows that both the sequence context and residual structure are important. There are [C]-dependent variations in the surface area for chemically identical groups such as the backbone or Ala. Consequently, the midpoints of transition of individual residues vary significantly (which we call the Holtzer effect) even though global folding can be described as an all-or-none transition. The collapse is specific in nature, resulting in the formation of compact structures with appreciable populations of nativelike secondary structural elements. The collapse transition is driven by the loss of favorable residue-solvent interactions and a concomitant increase in the strength of intrapeptide interactions with a decreasing [C]. The strength of these interactions is nonuniformly distributed throughout the structure of protein L. Certain secondary structure elements have stronger [C]-dependent interactions than others in the denatured state.

Dataset Information

The origin of ?-strand bending in globular proteins.

Publications

The origin of β-strand bending in globular proteins.

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